| 1. |
- Asenjo, Felipe A., et al.
(författare)
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Semi-relativistic effects in spin-1/2 quantum plasmas
- 2012
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 073042-
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Tidskriftsartikel (refereegranskat)abstract
- Emerging possibilities for creating and studying novel plasma regimes, e. g. relativistic plasmas and dense systems, in a controlled laboratory environment also require new modeling tools for such systems. This motivates theoretical studies of the kinetic theory governing the dynamics of plasmas for which both relativistic and quantum effects occur simultaneously. Here, we investigate relativistic corrections to the Pauli Hamiltonian in the context of a scalar kinetic theory for spin-1/2 quantum plasmas. In particular, we formulate a quantum kinetic theory for the collective motion of electrons that takes into account effects such as spin-orbit coupling and Zitterbewegung. We discuss the implications and possible applications of our findings.
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| 2. |
- Bartley, Andreas, et al.
(författare)
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The Swedish study of Irrigation-fluid temperature in the evacuation of Chronic subdural hematoma (SIC!) : study protocol for a multicenter randomized controlled trial
- 2017
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Ingår i: Trials. - : BIOMED CENTRAL LTD. - 1745-6215. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Background: Chronic subdural hematoma (cSDH) is one of the most common conditions encountered in neurosurgical practice. Recurrence, observed in 5-30% of patients, is a major clinical problem. The temperature of the irrigation fluid used during evacuation of the hematoma might theoretically influence recurrence rates since irrigation fluid at body temperature (37 degrees C) may beneficially influence coagulation and cSDH solubility when compared to irrigation fluid at room temperature. Should no difference in recurrence rates be observed when comparing irrigation-fluid temperatures, there is no need for warmed fluids during surgery. Our main aim is to investigate the effect of irrigation-fluid temperature on recurrence rates and clinical outcomes after cSDH evacuation using a multicenter randomized controlled trial design.Methods: The study will be conducted in three neurosurgical departments with population-based catchment areas using a similar surgical strategy. In total, 600 patients fulfilling the inclusion criteria will randomly be assigned to either intraoperative irrigation with fluid at body temperature or room temperature. The power calculation is based on a retrospective study performed at our department showing a recurrence rate of 5% versus 12% when comparing irrigation fluid at body temperature versus fluid at room temperature (unpublished data). The primary endpoint is recurrence rate of cSDH analyzed at 6 months post treatment. Secondary endpoints are mortality rate, complications and health-related quality of life.Discussion: Irrigation-fluid temperature might influence recurrence rates in the evacuation of chronic subdural hematomas. We present a study protocol for a multicenter randomized controlled trial investigating our hypothesis that irrigation fluid at body temperature is superior to room temperature in reducing recurrence rates following evacuation of cSDH.
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| 3. |
- de Frias, Cindy M., et al.
(författare)
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Influence of COMT Gene Polymorphism on fMRI-assessed Sustained and Transient Activity during a Working Memory Task
- 2010
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Ingår i: Journal of cognitive neuroscience. - Cambridge, Mass. : MIT Press. - 0898-929X .- 1530-8898. ; 22:7, s. 1614-1622
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Tidskriftsartikel (refereegranskat)abstract
- The catechol O-methyltransferase (COMT) gene-encoding an enzyme that is essential for the degradation of dopamine (DA) in prefrontal cortex (PFC)-contains a single nucleotide polymorphism (val/met) important for cognition. According to the tonic-phasic hypothesis, individuals carrying the low-enzyme- activity allele (met) are characterized by enhanced tonic DA activity in PFC, promoting sustained cognitive representations in working memory. Val carriers have reduced tonic but enhanced phasic dopaminergic activity in subcortical regions, enhancing cognitive flexibility. We tested the tonic-phasic DA hypothesis by dissociating sustained and transient brain activity during performance on a 2-back working memory test using mixed blocked/event-related functional magnetic resonance imaging. Participants were men recruited from a random sample of the population (the Betula study) and consisted of 11 met/met and 11 val/val carriers aged 50 to 65 years, matched on age, education, and cognitive performance. There were no differences in 2-back performance between genotype groups. Met carriers displayed a greater transient medial temporal lobe response in the updating phase of working memory, whereas val carriers showed a greater sustained PFC activation in the maintenance phase. These results support the tonic-phasic theory of DA function in elucidating the specific phenotypic influence of the COMT val(158)met polymorphism on different components of working memory.
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| 4. |
- Edlund, Jens, et al.
(författare)
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3rd party observer gaze as a continuous measure of dialogue flow
- 2012
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Ingår i: Proceedings of the 8th International Conference on Language Resources and Evaluation, LREC 2012. - Istanbul, Turkey : LREC. ; , s. 1354-1358
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Konferensbidrag (refereegranskat)abstract
- We present an attempt at using 3rd party observer gaze to get a measure of how appropriate each segment in a dialogue is for a speaker change. The method is a step away from the current dependency of speaker turns or talkspurts towards a more general view of speaker changes. We show that 3rd party observers do indeed largely look at the same thing (the speaker), and how this can be captured and utilized to provide insights into human communication. In addition, the results also suggest that there might be differences in the distribution of 3rd party observer gaze depending on how information-rich an utterance is.
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| 5. |
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Exhibition: Space Waves and a Tale : Hannes Alfvén (1908–1995). Nobel Prize laureate in physics 1970.
- 2022
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Konstnärligt arbeteabstract
- The exhibition Space Waves and a Tale presented parts of Alfvén's extensive research, his community engagement and last but not least, his fictional story The tale of the great computing machine from 1966. In 1970 KTH professor Hannes Alfvén (1908 – 1995) was awarded the Nobel Prize in physics for his discoveries and applications in plasma physics. The exhibition Space Waves and a Tale presented parts of Alfvén's extensive research, his community engagement and his fictional story The tale of the great computing machine from 1966.Alfvén's research allow us to explore all corners of the universe – from the auroras on earth to the auroras on other planets, from solar wind to stellar wind, from plasma phenomena in the laboratory to astrophysical plasma phenomena in ours and other galaxies.The tale of the great computing machine is a satirical tale that tells the story of a future society controlled by computers and is also the source of inspiration for an opera with the same name.As part of the exhibition Space Waves and a Tale visitors were invited to share their visions of how future technology will shape our lives and societies. Two students from the KTH School of Architecture have contributed to the exhibition by designing and building a flexible and sustainable exhibition module. Students from BOOMERANG REXUS participated with objects related to aerospace research.Space Waves and a Tale was produced by the project group for KTH 200 years anniversary celebration together with KTH Library, The Opera: The Tale of the Great Computing Machine, the Division of Space and Plasma Physics and the KTH School of Architecture.In connection with the exhibithion there was a book discussion, popular science lecture and a class visit.
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| 6. |
- Hammar, Petter, et al.
(författare)
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The lac repressor displays facilitated diffusion in living cells
- 2012
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 336:6088, s. 1595-1598
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Tidskriftsartikel (refereegranskat)abstract
- Transcription factors (TFs) are proteins that regulate the expression of genes by binding sequence-specific sites on the chromosome. It has been proposed that to find these sites fast and accurately, TFs combine one-dimensional (1D) sliding on DNA with 3D diffusion in the cytoplasm. This facilitated diffusion mechanism has been demonstrated in vitro, but it has not been shown experimentally to be exploited in living cells. We have developed a single-molecule assay that allows us to investigate the sliding process in living bacteria. Here we show that the lac repressor slides 45 ± 10 base pairs on chromosomal DNA and that sliding can be obstructed by other DNA-bound proteins near the operator. Furthermore, the repressor frequently (>90%) slides over its natural lacO(1) operator several times before binding. This suggests a trade-off between rapid search on nonspecific sequences and fast binding at the specific sequence.
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| 7. |
- Ilderton, Anton, et al.
(författare)
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Pair annihilation in laser pulses : Optical versus x-ray free-electron laser regimes
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - New York, N.Y. : Publ. by the American Physical Society through the American Institute of Physics. - 1050-2947 .- 1094-1622. ; 84:3, s. 032119-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the theory and phenomenology of pair annihilation, within an ultrashort laser pulse, to a single photon. The signature of this process is the unidirectional emission of single photons with a fixed energy. We show that the cross section is significantly larger than for two-photon pair annihilation in vacuum, with x-ray free-electron laser parameters admitting a much clearer signal than optical beams.
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| 8. |
- Klintfors, Eeva, et al.
(författare)
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Cortical N400-potentials generated by adults in response to semantic incongruities
- 2011
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Ingår i: Proceedings of Fonetik 2011. - Stockholm, Sweden : Universitetsserveice AB. ; , s. 121-124
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Eight adult participants were investigated in a pre-experiment for the future assessment of semantic N400 effects in children. The materials were words resented in semantically incongruent vs. congruent picture contexts. For example, he word duck was played while a picture of a tree was shown in the incongruent est condition vs. the word duck was played while a picture of a duck was shown in the congruent test condition. A larger N400 effect was expected in response to the incongruent audio-visual pairings. The results showed in time extended peak-to peak differences between congruent and incongruent audio-visual pairings at the centroparietal, parietal and parieto-occipital recording sites. This study was performed to validate the current materials to be used to answer questions on appearance of the N400 component in children.
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| 9. |
- Kompus, Kristiina, 1983-, et al.
(författare)
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Distinct control networks for cognition and emotion in the prefrontal cortex
- 2009
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Ingår i: Neuroscience Letters. - : Elsevier BV. - 0304-3940 .- 1872-7972. ; 467:2, s. 76-80
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Tidskriftsartikel (refereegranskat)abstract
- The activation of dorsolateral prefrontal cortex (dlPFC) has been suggested to reflect the engagement of a control mechanism for top-down biasing of context processing in resource-demanding memory tasks. Here we tested the hypothesis that the dlPFC subserves a similar function also in attention and emotion tasks. 18 healthy young adults were tested in a functional magnetic resonance imaging (fMRI) study where the demands for context processing were manipulated in three different cognitive domains: auditory attention, episodic retrieval, and emotion regulation. We found that the right dlPFC was jointly sensitive to increased cognitive demands in the attention and memory tasks. By contrast, increased demands in the emotion task (reappraisal) were associated with increased activity in ventromedial PFC along with decreased amygdala activity. Our findings of divergent prefrontal control networks for cognitive and emotional control extend previous separations of cognition and emotion in the anterior cingulate cortex.
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| 10. |
- Lansner, Anders, et al.
(författare)
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Reactivation in Working Memory : An Attractor Network Model of Free Recall
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:8, s. e73776-
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic nature of human working memory, the general-purpose system for processing continuous input, while keeping no longer externally available information active in the background, is well captured in immediate free recall of supraspan word-lists. Free recall tasks produce several benchmark memory phenomena, like the U-shaped serial position curve, reflecting enhanced memory for early and late list items. To account for empirical data, including primacy and recency as well as contiguity effects, we propose here a neurobiologically based neural network model that unifies short- and long-term forms of memory and challenges both the standard view of working memory as persistent activity and dual-store accounts of free recall. Rapidly expressed and volatile synaptic plasticity, modulated intrinsic excitability, and spike-frequency adaptation are suggested as key cellular mechanisms underlying working memory encoding, reactivation and recall. Recent findings on the synaptic and molecular mechanisms behind early LTP and on spiking activity during delayed-match-to-sample tasks support this view.
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